Correcting the
American Heart Association on Outdated Food Combining Theories
The
American Heart Association recently published a letter from John
McDougall MD
Volume 105, Number 25; June 25, 2002 page 197
Plant
Foods Have a Complete Amino Acid Composition
The
American Heart Association (AHA) Science Advisory, “Dietary
Protein and Weight Reduction: A Statement for Health-care Professionals
From the Nutrition Committee of the Council on Nutrition, Physical
Activity, and Metabolism of the American Heart Association,”
contains often quoted, but incorrect, infor-mation about the adequacy
of amino acids found in plant foods.1 This report states, “Although
plant proteins form a large part of the human diet, most are deficient
in 1 or more essential amino acids and are therefore regarded
as incomplete proteins.”
William
Rose and his colleagues completed research by the spring of 1952
that determined the human requirements for the 8 essential amino
acids.2 They set as the “minimum amino acid requirement”
the largest amount required by any single subject and then they
doubled these values to make the “recommended amino acid
requirement,” which was also considered a “definitely
safe intake.” By calculating the amount of each essential
amino acid provided by unprocessed complex carbohydrates (starches
and vegetables)3 and comparing these values with those determined
by Rose,1 the results show that any single one or combination
of these plant foods provides amino acid intakes in excess of
the recom-mended requirements. Therefore, a careful look at the
founding scientific research and some simple math prove it is
impossible to design an amino acid– deficient diet based
on the amounts of unprocessed starches and vegetables sufficient
to meet the calorie needs of humans. Furthermore, mixing foods
to make a complementary amino acid composition is unnecessary.4
The
reason it is important to correct this misinformation is that
many people are afraid to follow healthful, pure vegetarian diets—they
worry about “incomplete proteins” from plant sources.
A vegetarian diet based on any single one or combination of these
unprocessed starches (eg, rice, corn, potatoes, beans), with the
addition of vegetables and fruits, supplies all the protein, amino
acids, essential fats, minerals, and vitamins (with the exception
of vitamin B12) necessary for excellent health. To wrongly suggest
that people need to eat animal protein for nutrients will encourage
them to add foods that are known to contribute to heart disease,
diabetes, obesity, and many forms of cancer, to name just a few
common problems.5
John
McDougall, MD
The McDougall Program
Santa Rosa, CA 95404
drmcdougall@drmcdougall.com
1.
St Jeor S, Howard B, Prewitt E. Dietary protein and weight reduction:
a statement for healthcare professionals from the Nutrition Committee
of the Council on Nutrition, Physical Activity, and Metabolism
of the American Heart Association. Circulation. 2001;104:1869
–1874.
2. Rose W. The amino acid requirement of adult man. Nutr Abst
Rev. 1957;27:631– 647.
3. Pennington J. Bowes’ & Church’s Food Values of
Portions Commonly Used. 17th ed. Philadelphia, Pa: Lippincott;
1998.
4. M. Irwin, Hegsted D. A conspectus of research on protein requirements
of man. J Nutr. 1971;101:385– 428.
5. Weisburger J. Eat to live, not live to eat. Nutrition. 2000;16:767–773.
AHA
Published Response
We
thank Dr McDougall for the thoughtful comments about the amino acid
composition of plant foods. The American Heart Association (AHA)
believes that vegetarian diets can be healthy, and we do not suggest
that people need to eat animal protein exclusively for nutrients.
You are correct that the reference to plant protein as being regarded
as incomplete is often quoted, but we did carefully state that “most”
are deficient in one or more essential amino acids and emphasized
that there is an optimum ratio of essential amino acids that determines
protein quality. The recommendation for mixing complementary vegetable
protein sources to maximize the diet is an important principal on
which vegetarian diets are based. Although an indiscriminate mixture
of plant proteins could meet protein amino acid requirements, it
must be remembered that the amino acid content in most plant proteins
is more limited in amount per serving than that from animal sources.
Thus, it is difficult to maintain essential amino acids at optimum
quantity and distribution. We certainly agree with Dr McDougall
that a vegetarian diet based on the AHA guidelines of 5 to 6 servings
of whole grains and 5 or more servings of vegetables and fruit would,
in fact, supply all of the amino acids necessary for health.
Barbara
V. Howard, PhD
MedStar Research Institute
108 Irving St NW
Washington, DC 20010
Barbara.v.howard@medstar.net
Dr.
McDougall Replies
Dear Sirs:
Last week the
American Heart Association Journal Circulation published a letter
to the editor by John McDougall, MD that corrected one of the most
common, yet damaging, myths about a healthy vegetarian diet - the
myth that plants do not contain adequate amounts of all the essential
amino acids. You will find this letter in Volume 105, Number 25;
June 25, 2002 on page 197 of the journal Circulation.
This letter
was written in response to an article published in Circulation,
October 9, 2001, by the Nutrition Committee of the Council on Nutrition,
Physical Activity, and Metabolism of the American Heart Association.
Misinformation printed in this influential journal has the ultimate
effect of condemning people to unhealthy diets based around meat
and other animal products, in order to get "adequate protein
and amino acids."
Rather than
admit their error, the response to Dr. McDougall's letter from one
of the key authors, Barbara Howard, PhD, was a thinly veiled attempt
to save face. In her short paragraph she contradicts herself by
declaring Dr. McDougall both right and wrong, and fails to sight
one scientific article to support her viewpoint that plant foods
are inadequate nutrition and fall short of meeting human needs for
protein and essential amino acids.
Even though
"mixing vegetable protein sources to maximize the diet is an
important principal on which vegetarian diets are based," this
belief is incorrect and can easily be corrected by a careful look
at the founding scientific research on human protein needs cited
by Dr. McDougall.
Please give
this important issue your attention, because it could make a real
difference in people's lives.
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